In this experiment we will learn about the spectroscope and how It works. To learn the concept of quantitative measurements, to construct a spectroscope and, to use it for taking quantitative measurements. Experimental Questions: Please complete this section of your write-up as you work on the experimental portion of this lab. 1. Hold the grating several inches from your face, at an angle. Look at the grating that you will be using. Describe what you see at the grating surface.
I see different color of the rainbow and when I change the angle that am holding the diffraction grating Hold the grating up to your eye and look through it. Describe what you see. Be specific. When I look to the light source directly, I see the rainbow either to the right or to the left of the light inlet slit. Before mounting your grating, look through the opening that you made for your 2. Grating. Describe what you see across the back of your spectroscope. I see the other opening that I made to be the light Inlet.
With the Grating now mounted, look through your spectroscope and describe what o see across the back of your spectroscope. Be specific. As I mentioned before, I can see the rainbow either to the right or to the left inside the box but when I look directly to the light source it look normal. Them all! The first color to the left of the rainbow will be dark blue or black, then purple, light blue, green, yellowish, yellow, orange, and finally red. 3. When you view the spectrum, you should be able to see a spectral image to the right of the slit and to the left of the slit.
How are the spectral images the same? The start with the same color and end with the same color also. So the one on the right start (from the close side of the light inlet) with dark blue and end with read, the one on the left will start (from the close side of the light inlet) also with dark blue and end with the red. How are they different? I don’t see really different between them but the one to the left looks shorter (in length) than the one on the right. 4. How does narrowing the slit affect the spectra that you are viewing (Try it and see! ? Compare the shape, thickness, and resolution of the spectral lines before and after narrowing the slit. The narrower the slit opening is, the clearer the black lines between the spectra colors. 5. Looking through the grating, view the scratches you made on the light rod. Do they look like they “glow? ” I didn’t make any scratches!!!! But among the light rod I print and tape the spectra looks like glowing a little bit. Now place your hand around the light rod. What effect does this have on the “glow? ” It makes it disappear completely. Effect does this have on the “glow? ” The black lines between my spectra disappear and the glow is no more there. Please briefly describe how your spectroscope works (This should only be 2-4 sentences. You should mention things like slit, grating, light rod, light, spectrum, … ). When the light inter through the like slit which makes it focused Just into that slit, after that the light breaks to parallel lines and by looking into the grating we see those colors clearly and we can measure the wave length by using the light rod. Calibration: 1.
A simple picture Draw your light rod, then draw the complete fluorescent visible spectra superimposed on the light rod, exactly as you see it in your spectroscope. Pick] 2. Now translate the picture above into a graphical representation of the data Draw the Hag spectral lines (show only the violet, green, and yellow lines that you see in the fluorescent spectrum) where they occur on your light rod. [Pick] Label each line with its wavelength 3. How many spaces from the center of violet line to center of green line? 2 spaces. How many spaces from the center of violet line to center of yellow line? Spaces. = difference in wavelength of spaces between two lines Using the violet and green lines: 2 50 Using the violet and yellow lines: 3 ) = 48 Average NM/space: (value #1 *value = (50+48)/2 – Agreement of the two values: NM/space (value#l) NM/space (value#2) 49 NM/space % difference = 100 x Value 1 – value 21/(average value) = lox 50 -481/(49 is this value < 10%_Yes_. ( go through calibration process until you can say "yes. ") Your spectroscope is now calibrated. Do not move the light rod - tape in place with clear tape if you have not yet done so.
In event that light rod moves, place reference mark in center of violet line, and re-secure light rod. Questions and Conclusions: Now that you better understand the functioning of a spectroscope, answer the allowing questions. 1. What is white light? White light is mixture of all color in spectra. What experimental evidence do you personally have to support this idea? (BY looking to the white light (light source) of my light spectra I saw the rainbow colors coming out from this white light and from this I can tell the white light is consist of all the colors. . The violet Hag emission spectral line at 436 NM was used as the reference in calibrating your spectroscope. Look in your textbook or other information source. What is the wavelength range for violet light? It’s between 380 and 450. If you are viewing a spectrum from another light source, and it has a violet line, I think my answer for this question will be kind of yes, because even if we are using different light source our spectrum should give us the same reading or range for our lights.
If it is not centered on the reference mark, what can you conclude about the wavelength of this new violet line? The reason can be that this source of light contain different amount(lines) of colors than the original source I used and it might have more violet color than the original source I used. Should you move your light rod? Why or why not? No, because we Just calibrated our spectrum and it should give us good reading for any light source. 3. Now that you have calibrated your light rod, list the wavelengths for each colored line that you see in the spectrum of your fluorescent light. See “Help Me!! ” section at the end of this lab for help). You can use the picture you drew in question 1 of the calibration procedure to get spaces from reference line for each color, and use your final calculated calibration value (NM/space). Your calibration value in NM/space: 49 I color Spaces from reference space + O spaces x your calibration value Mann+ (1*49) = inner I sonar + inner 1 inner inner I Wavelength = 436 + spaces x NM/ I I violet 10 = Mann Inman I Bobbie II I I Light Green 12 I Dark Green 12 Loraine 13 Inman inner Help Me!! Figuring wavelengths using a calibrated light rod: This is an e-mail that I sent to a student last quarter. She had already figured out how many NM each light rod division was worth, but did not know how to use the information to fugue out the wavelengths of specific lines on her spectral grids. My reply was as follows: Student, When you figured out the number of wavelengths each spacing was worth, you got cost of the info you needed to answer this question. You know that your reference line is at 436 NM, you know how many manometers each space in the light rod is, and now you can use it like a ruler.
You drew an accurate representation of your spectra, with the spaces as marked in your light rod. You can go through and label each spacing line with its nanometer. For example we know the reference line is at 436 NM, and let’s say that in the calibration section you calculated a calibration value of 22 NM/space- this means that the spaces are each 22 NM apart spectrally. The preference is at 436 NM, then the next spacing line is at (436+22) NM or 458 NM. The next line after that is (458+22) NM or Mann. And so on…
Now look where the colors change. For example, look where you go from Purple to blue on the incandescent spectral grid. If it falls on a spacing line then you pretty much know what it is. If it falls between two spacing lines, you need to make your best estimate of what it is. Going back to the above example, if on your spectral grid, the Purple/blue transition occurs 3/4 of the way between the 436 and 458 NM spacing lines, then you would estimate that the transition occurs at (Mann + (3/4 space) NM/space) NM вЂ? (436+18. ) NM = 454. 5 NM. You would do this for each color transition that you can identify. Some people saw distinct color bands separated by black spaces for the Fluorescent light. If there is not a smooth transition between colors, but rather spaces between the colors, then you would identify the edge of each color band. You would find the wavelength for the beginning and end of each color band Just like above. I hope that that helps you figure out the wavelengths. If you still need more help, let me know.